Over the past few years, advances in network transmission have facilitated an explosive increase in data transmission rate. And in data transmission nowadays, it is advantageous to transmit signals over a pair of conductors, which is recognized as “differential pair”, rather than over a single conductor. The way it works is having signals transmitted on each conductor with equal magnitudes but opposite phases. Data transmission using differential pair technique is acknowledged as balanced transmission. Comparing to single-ended transmission, differential signals are generally more immune to the effects of external electrical noises. And usually, the two conductors of a differential pair for network transmission are twisted in a precisely managed ratio. The well-controlled twists increase the noise immunity and reduce the bit error rate (BER) of data transmission.
Considering the ascendency of differential copper cabling in the market today, the standards have been continuously focusing on keeping the same user-friendly RJ-45 connector interface allowing for backward compatibility. The RJ-45 connector was originally adopted as a standard specified interface of network connectors back in 1991 when the data transmission speed was set to 10 Mbs/sec with operating frequency up to 16 MHz only, which was referred to as Category 3.
Now, the most up-to-date Augmented Category 6 standards (e.g. TIA-568-C.2 & ISO-11801 ed.2) compliance with IEEE 802.3an 10GBASE-T protocol is set to use RJ-45 connector remains. However, the transmission speed is specified 1,000 times higher (10 Gbs/sec) with operating frequency up to 500 MHz. Using RJ-45 connectors at high frequencies leads to extreme challenges due to the crosstalks and losses come along with the fixed RJ-45 geometry.
When it comes to qualification of transmission capability of a RJ-45 modular jack or patch panel connecting hardware (hereinafter referred to as “jack”), there are two types of measurements need to be taken into consideration. They are transmission (crosstalk) and reflection (loss). Among the transmission requirements specified by standard, near end crosstalk (NEXT), far end crosstalk (FEXT), and insertion loss (IL) are the key parameters which have to be satisfied while return loss (RL) is the parameter determined with a reflection measurement.
Energy from one signal conductor may be partially introduced to couple into adjacent signal conductor by the electric field generated between two signal conductors and the magnetic field generated owing to the variation of electric field simultaneously. This capacitive and inductive coupling represents the phenomenon of crosstalk. Crosstalks are the unwanted signals electromagnetically coupled from another conductor unintentionally. Therefore, those distortional signals usually affect the signals that are supposed to run through the disturbed differential signal path.
Crosstalk comes from the legacy of RJ-45 modular plug (hereinafter referred to as “plug”), which has a significant amount of crosstalk coupling (NEXT and FEXT) when being mated with a jack. The standard RJ-45 jack housing utilizes a straightforward design with a spaced interval 1.016 mm of resilient pins from 1 to 8 in a relative uniform and parallel alignment (FIG. 1).
Among the wire pairs that are crimped with contact blades proximally inside the plug, capacitive and inductive couplings are parasitized therein. The contact blades have a large area to react themselves as a transmitting and receiving antenna. And the split of wire pair positioned in contact 3 and contact 6 worsens all the pair combinations by coupling adjacent three other pairs. Among all the signal interference, the near end coupling between Pair 1 and Pair 3 is the most severe one due to the Pair 3 is diverged and physically enfold the Pair 1 (FIG. 2). Therefore, when a RJ-45 jack is connected to a RJ-45 plug to transmit high-frequency data signals, crosstalks generated and reflected losses caused by impedance mismatches right at the mating area increase dramatically. Especially high NEXT and FEXT are produced for certain adjacent wire pairs therein. It all makes sense because the mated resilient pin 3 (tip) is closer to the mated resilient pin 4 (ring) than is to the mated resilient pin 5 (tip). Likewise, the mated resilient pin 6 (ring) is closer to the mated resilient pin 5 (tip) than is to the mated resilient pin 4 (ring)(FIG. 3). Consequently differential capacitive and inductive couplings occurs between the mated Pair 1 and Pair 3 that generate hugely both NEXT and FEXT.
A RJ-45 jack that is configured to suppress or to compensate for crosstalk introduced by a mating RJ-45 plug, is generally known. The way to relieve crosstalk problem is conceptually performed by employing capacitive and inductive couplings equal to and opposite to the noise signals such that the induced noise signals are effectively cancelled by the induced correction signals. This implementation is referred to as “compensation”. In other words, if electromagnetic compensation inside a modular jack is in opposite polarity and substantially equal in magnitude to a modular plug, a balanced differential signal transmission can be achieved.
Referring to FIG. 4, the NEXT vector of a RJ-45 standard specified plug derived from standard specified method is demonstrated. Obviously, Pair 1 and Pair 3 have to be capacitively and inductively compensated the most so as to enable desirable balanced transmission.
Accordingly, it is imperative to provide a pin structure of a modular jack to reduce crosstalk and loss and thereby meet strict standards.